1. Field of the Invention
The present invention relates generally to an image forming apparatus. More particularly, the present invention relates to a fuser cooling fan control method for varying the operation timing of the cooling fan for cooling a fusing unit according to the surrounding environment (that is, temperature and/or humidity) and an image forming apparatus having the same.
2. Description of the Related Art
In an electro-photographic image forming apparatus, a color or monochromatic image formed by an image forming unit is transferred onto printing paper by a transfer unit. The image is fixed onto the paper through a fixing unit, and the paper with the image is then discharged. The fixing unit applies high heat and high pressure to the paper where the image is to be transferred. Because of the high heat and pressure, the fixing unit can get overheated. To prevent overheating of the fixing unit, the image forming apparatus employs a fuser cooling fan for cooling the fixing unit.
As shown in a timing chart in FIG. 1, the cooling fan is turned on/off, interlockingly with the on/off state of the image forming apparatus. That is, when the power of the image forming apparatus is turned on, the cooling fan is also turned on and running. On the other hand, when the image forming apparatus is in sleep mode, the cooling fan remains turned off until a printing operation of the apparatus is initiated.
Because the on/off state of the above-described fuser cooling fan in the image forming apparatus is controlled by the power on/off mode of an image forming apparatus, irrespective of the surrounding environment (that is, temperature and/or humidity), an image fixing defect may be caused.
For example, when the ambient temperature and/or humidity of the image forming apparatus is at or lower than room temperature (10-32° C.) and normal humidity (30-80%), printing using paper and developer occurs at a relatively low temperature because the cooling fan runs from the initial phase of the printing process. Thus, the printing paper is not sufficiently heated, and an image fixing defect occurs.